This application claims the priority of German patent 198 38 745.8, filed Aug. 26, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a slide bearing, particularly as a crankshaft main bearing of an internal-combustion engine, having a bearing block and a bearing cap. The invention also relates to a process for manufacturing a slide bearing.
Divisible slide bearings, particularly as crankshaft main bearings, are generally known into which a bush made of a typical slide bearing material or a metal sheet coated with such a material is inserted. These bushes or sheet metal inserts, which must also be constructed in a divisible manner, permit a uniform distribution of the bearing load over the bearing surface of the bearing eye. However, oil carbon can easily form between the inserted bushes and the bearing eye or the shaft.
Furthermore, the bushes compensate for machining inaccuracies which can virtually not be avoided when the bearing eye is manufactured. Particularly if the materials of the bearing block and of the bearing cap differ--for example, between an aluminum diecast bearing block of a crankshaft main bearing constructed in one piece with the crankcase and a steel cast bearing cap--the manufacturing of a round bearing eye is virtually impossible. In order to be able to machine the bearing eye, the bearing cap and the bearing block of the respective bearing are already joined before the machining. For this reason, for example, during the turning or during the mandrel honing, the blades of the machining tool must be able to machine aluminum as well as steel in the same cut. Because of the different characteristics of the materials of the bearing cap and of the bearing block, particularly the required cutting forces, after the machining, the bearing eyes always deviate slightly from a round shape (e.g., the bearing eyes may have an oval shape).
German Patent Document DE 43 03 592 A1 indicates that it is possible to do completely without a bearing bush. It illustrates a connecting rod to which a special bearing layer is applied in the area of its finished bearing eyes. Then, the connecting rod, together with the bearing layer, is separated by cracking, and connecting rod eyes are obtained which are ready to be mounted, are divided into two parts and have ideal bearing characteristics by means of the coating with a bearing layer made of a suitable bearing material. A similar technique is described in German Patent Document DE 26 56 203 C2.
Since, however, in the case of connecting rods, both parts of the bearing eyes, thus the bearing cover and the bearing block, consist of the same material, no problems or only slight problems occur with respect to deviations from roundness caused by the manufacturing.
It is therefore an object of the invention to provide a slide bearing with a divisible bearing eye, in which a bearing block and a bearing cap are made of different materials, and which has minimal deviations from roundness of the bearing eye and ideal bearing characteristics. It is also an object of the invention to provide a process for manufacturing such a slide bearing.
According to the invention, these and other objects have been achieved by a slide bearing for an internal-combustion engine, comprising: a bearing block; and a bearing cap, the bearing block and the bearing cap being made of different materials, each of the bearing block and the bearing cap having a bearing surface wherein the slide bearing has a bearing layer made of a bearing material which is fixedly connected with the slide bearing, the bearing layer at least approximately completely covering the bearing surfaces of the bearing cap and of the bearing block.
According to the invention, these and other objects have been achieved by an internal-combustion engine crankcase, comprising the slide bearing of claim 1 as a crankshaft main bearing.
According to the invention, these and other objects have been achieved by a method of manufacturing a slide bearing, for an internal-combustion engine, having a bearing block and a bearing cap, the bearing block and the bearing cap being made of different materials, said method comprising: the bearing cap and the bearing block of the slide bearing with one another; machining bearing surfaces of a bearing eye of the slide bearing such that a maximal roundness deviation remains which is smaller than a desired thickness of a planned bearing layer; applying the bearing layer to the bearing surface of the bearing eye; cracking the bearing layer and demounting the bearing cap from the bearing block; reconnecting the bearing cap and the bearing block of the slide bearing with one another; and machining the bearing layer.
The coating of the bearing with a bearing layer made of a suitable bearing material provides ideal bearing characteristics of the slide bearing and the generation of noise can clearly be reduced. In addition, an oil carbon formation can be prevented by means of the bearing layer fixedly connected with the bearing eye.
The parts of the slide bearing, specifically the bearing block and the bearing cap, which are fixedly connected with one another for a machining of the bearing eye, after the machining, are very advantageously coated with a bearing layer made of a bearing material, this bearing material generally being softer than the material of the bearing cap and of the bearing block. The bearing layer is advantageously applied so that its layer thickness is larger than the maximal roundness deviations which have remained after the mechanical machining of the bearing eye. After the demounting of the bearing cap, in which case the soft bearing layer is broken apart (cracked), the bearing cap is again mounted on the bearing block. The precision machining, which follows, for example, precision turning or mandrel honing, can thus take place under very advantageous conditions. Since only portions of the previously applied soft bearing layer are removed, the cutting forces remain low and homogeneous cutting conditions exist along the complete surface of the bearing eye, whereby high manufacturing accuracies can be achieved.
During the mounting after the cracking of the bearing layer, burrs may possibly occur on the abutting surfaces of the bearing layer which now project into the interior of the bearing eye. During the precision machining of the bearing eye, any burrs which occur are removed again. Thus a bearing eye is obtained which has a homogeneous bearing surface and very low deviations from roundness.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.